Irrigated catheter with internal position sensor

ABSTRACT

A catheter carries a position sensor in a distal, on-axis position in an irrigated ablation tip electrode. The tip electrode has a shell wall that defines a cavity through which fluid flows and exits via fluid ports formed in the shell wall. The cavity is sealed by an internal member extends into the cavity with a baffle portion and a distal portion. The distal portion safely houses the position sensor and the baffle portion diffuses and disperses fluid entering the tip electrode for a more uniform flow through the cavity. The distal portion is configured to provide an annular region that runs along the length of the tip electrode to better feed fluid to the more distal fluid ports on the tip electrode for more uniform cooling at all locations on the tip electrode.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application is a continuation of and claims priority to andthe benefit of U.S. patent application Ser. No. 12/767,763 filed Apr.26, 2010, now issued as U.S. Pat. No. 9,949,791, the entire content ofwhich is incorporated herein by reference.

FIELD OF INVENTION

The present invention relates to an electrophysiologic catheter that isparticularly useful for ablation and sensing electrical activity ofheart tissue.

BACKGROUND OF INVENTION

Electrode catheters have been in common use in medical practice for manyyears. Diagnosis and treatment of cardiac arrythmias by means ofelectrode catheters include mapping the electrical properties of hearttissue and selectively ablating cardiac tissue by application of energy.Such ablation can cease or modify the propagation of unwanted electricalsignals from one portion of the heart to another. The ablation processdestroys the unwanted electrical pathways by formation of non-conductinglesions. Various energy delivery modalities have been disclosed forforming lesions, and include use of microwave, laser and more commonly,radiofrequency energies to create conduction blocks along the cardiactissue wall.

In a two-step procedure—mapping followed by ablation—electrical activityat points within the heart is typically sensed and measured by advancinga catheter containing one or more electrical sensors (or electrodes)into the heart, and acquiring data at a multiplicity of points. Thesedata are then utilized to select the tissue target areas at whichablation is to be performed.

In use, the electrode catheter is inserted into a major vein or artery,e.g., the femoral artery, and then guided into the chamber of the heartwhich is of concern. A reference electrode is provided, generally tapedto the patient's skin. Radio frequency (RF) current is applied to thetip electrode, and flows through the surrounding media, i.e., blood andtissue, toward the reference electrode. The distribution of currentdepends on the amount of electrode surface in contact with the tissue,as compared to blood which has a higher conductivity than the tissue.

Heating of the tissue occurs due to its electrical resistivity. Thetissue is heated sufficiently to cause cellular destruction in thecardiac tissue resulting in formation of a lesion within the cardiactissue which is electrically non-conductive. During this process,heating of the electrode also occurs as a result of conduction from theheated tissue to the electrode itself. If the electrode temperaturebecomes sufficiently high, possibly above 60° C., a thin transparentcoating of dehydrated blood can form on the surface of the electrode. Ifthe temperature continues to rise, this dehydrated layer of blood canbecome progressively thicker resulting in blood coagulation on theelectrode surface. Because dehydrated biological material has a higherelectrical resistance than tissue, impedance to the flow of electricalenergy into the tissue also increases. If the impedance increasessufficiently, an impedance rise occurs and the catheter must be removedfrom the body and the tip electrode cleaned.

In a typical application of RF current, circulating blood provides somecooling of the ablation electrode. Another method is to irrigate theablation electrode, e.g., with physiologic saline at room temperature,to actively cool the ablation electrode instead of relying on the morepassive physiological cooling provided by the blood. Because thestrength of the RF current is no longer limited by the interfacetemperature, current can be increased. This results in lesions whichtend to be larger and more spherical, usually measuring about 10 to 12mm.

The clinical effectiveness of irrigating the ablation electrode isdependent upon the distribution of flow within the electrode structureand the rate of irrigation flow through the tip. Effectiveness isachieved by reducing the overall electrode temperature and eliminatinghot spots in the ablation electrode which can initiate coagulumformation. More channels and higher flows are more effective in reducingoverall temperature and temperature variations, i.e., hot spots. Thecoolant flow rate must be balanced against the amount of fluid that canbe injected into the patient and the increased clinical load required tomonitor and possibly refill the injection devices during a procedure. Inaddition to irrigation flow during ablation, a maintenance flow,typically a lower flow rate, is required throughout the procedure toprevent backflow of blood into the coolant passages. Thus, reducingcoolant flow by utilizing it as efficiently as possible is a desirabledesign objective.

Another consideration is the ability to control the exact position andorientation of the catheter tip. This is ability is critical and largelydetermines the usefulness of the catheter. It is generally known toincorporate into electrophysiology catheters an electromagnetic (EM)tri-axis location/position sensor for determining the location of acatheter's distal end. An EM sensor in the catheter, typically near thecatheter's distal end within the distal tip, gives rise to signals thatare used to determine the position of the device relative to a frame ofreference that is fixed either externally to the body or to the heartitself. The EM sensor may be active or passive and may operate bygenerating or receiving electrical, magnetic or ultrasonic energy fieldsor other suitable forms of energy known in the art.

U.S. Pat. No. 5,391,199, the entire disclosure of which is incorporatedherein by reference, describes a position-responsive catheter comprisinga miniature sensor coil contained in the catheter's distal end. The coilgenerates electrical signals in response to externally-applied magneticfields, which are produced by field-generator coils placed outside thepatient's body. The electrical signals are analyzed to determinethree-dimensional coordinates of the coil.

U.S. Pat. No. 6,690,963, the entire disclosure of which is herebyincorporated by reference, is directed to a locating system fordetermining the location and orientation of an invasive medicalinstrument, for example a catheter or endoscope, relative to a referenceframe, comprising: a plurality of field generators which generate known,distinguishable fields, preferably continuous AC magnetic fields, inresponse to drive signals; a plurality of sensors situated in theinvasive medical instrument proximate the distal end thereof whichgenerate sensor signals in response to said fields; and a signalprocessor which has an input for a plurality of signals corresponding tosaid drive signals and said sensor signals and which produces the threelocation coordinates and three orientation coordinates of a point on theinvasive medical instrument.

Because of the size of the tip electrode and the limited interior spacetherein, the EM sensor is often positioned outside of the tip electrode,proximally thereof, and often off axis from the tip electrode which canreduce the accuracy of the position sensing capabilities of the sensor.Being outside the tip electrode, the position sensor is also exposed tobending stresses and can limit the flexibility and deflection of thedistal tip section. Moreover, the sensor can be damaged by RF energyduring ablation.

Where the distal tip is irrigated, the efficiency of irrigated coolingbecomes a significant factor as ablation procedures can last five or sixhours resulting in extensive fluid-loading in the patient. Conventionalirrigated tip electrodes typically operate with a flow rate of about 17ml/minute at below about 30 watts of RF ablation energy to about 30-50ml/minute at about 30 watts or greater. The limited space in the distaltip may also lead to anchoring of the puller wires to a less desirablelocation such as a tubing wall causing tearing of the tubing wall and/orunintended asymmetrical deflection.

Accordingly, it is desirable that a catheter be adapted for mapping andablation with improved cooling and position sensing characteristics byproviding a tip configuration that includes housing in which theposition sensor is protected and is located both distally and on-axiswithout inhibiting the flow and dispersion of irrigation fluid throughthe tip. It is also desirable that such a catheter exhibit symmetricalbi-directional deflection and that the walls of the catheter be damagedfrom deflection puller wires.

SUMMARY OF THE INVENTION

The present invention is directed to a catheter adapted for mapping andablating heart tissue that carries a position sensor in a distal,on-axis position in an irrigated ablation tip electrode. The catheter ofthe present invention has an elongated catheter body and a deflectablesection distal the catheter body. The tip electrode has an internalconfiguration that promotes fluid diffusion and dispersion.

In one embodiment, the tip electrode has a shell wall that defines acavity through which fluid flows and exits via fluid ports formed in theshell wall. The cavity is sealed by an internal member extends into thecavity with a baffle portion and a distal portion. The distal portionsafely houses the position sensor and the baffle portion diffuses anddisperses fluid entering the tip electrode for a more uniform flowthrough the cavity. The distal portion is configured to provide anannular region that runs along the length of the tip electrode to betterfeed fluid to the more distal fluid ports on the tip electrode for moreuniform cooling at all locations on the tip electrode.

In a more detailed embodiment, the baffle portion has a cross-sectionnonconforming to an inner space of the shell so that separate anddistinct axial flow paths are provided to slow axial momentum of thefluid entering the tip electrode. For example, where the inner space ofthe shell is generally circular, the baffle portion has a polygonal(regular or irregular) cross-section upon which fluid impinges whenentering the cavity of the tip electrode. Additionally, the passage bywhich fluid enters the cavity has an elongated cross-section for moreefficient use of space inside the tip electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will bebetter understood by reference to the following detailed descriptionwhen considered in conjunction with the accompanying drawings wherein:

FIG. 1 is a side view of an embodiment of a catheter of the presentinvention.

FIG. 2A is a side cross-sectional view of the catheter FIG. 1, showing ajunction between a catheter body and a deflectable intermediate section,taken along a first diameter.

FIG. 2B is a side cross-sectional view of the catheter of FIG. 1,showing a junction between a catheter body and a deflectableintermediate section, taken a long a second diameter generallyperpendicular to the first diameter.

FIG. 2C is a longitudinal cross-section view of the deflectableintermediate section of FIGS. 2A and 2B taken along line c—c.

FIGS. 3A-3C are schematic diagrams of an embodiment of a control handleshowing the catheter in the neutral and deflected positions.

FIG. 4 is a top plan view of an embodiment of a control handle,including a deflection control assembly.

FIG. 5 is a partial side perspective view of an embodiment of adeflection arm and a tension adjustment knob as mounted on a controlhandle.

FIGS. 6A and 6B are perspective top and bottom views of an embodiment ofa rocker member as used in a deflection control assembly.

FIG. 7 is a side elevational view of an embodiment of a pulley as usedin a deflection control assembly.

FIG. 8 is an exploded perspective view of an embodiment of a tipelectrode assembly.

FIG. 9 is a cross sectional perspective view of an embodiment of a tipelectrode assembly.

FIG. 9A is a longitudinal cross sectional view of the tip electrodeassembly of FIG. 9, taken along line a—a

FIG. 9B is a longitudinal cross sectional view of the tip electrodeassembly of FIG. 9, taken along line b—b

FIG. 9C is a longitudinal cross sectional view of the tip electrodeassembly of FIG. 9, taken along line c—c

FIG. 9D is a longitudinal cross sectional view of the tip electrodeassembly of FIG. 9, taken along line d—d

FIG. 9E is a longitudinal cross sectional view of the tip electrodeassembly of FIG. 9, taken along line e—e

FIG. 9F is a longitudinal cross sectional view of the tip electrodeassembly of FIG. 9, taken along line f—f

FIG. 10 is an exploded perspective view of an alternate embodiment of atip electrode assembly.

FIG. 10A is an end cross-sectional view of an alternate embodiment of aninternal member.

FIG. 10B is an end cross-sectional view of another alternate embodimentof an internal member.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates an embodiment of a catheter 10 with improved positionsensing and cooling capabilities. The catheter has an elongated catheterbody 12 with proximal and distal ends, an intermediate deflectablesection 14 at the distal end of the catheter body 12, and a distalsection 15 with an irrigated mapping and ablation tip electrode 17. Thecatheter also includes a control handle 16 at the proximal end of thecatheter body 12 for controlling bi-directional deflection of theintermediate section 14. Advantageously, the tip electrode 17 houses anelectromagnetic position sensor in a distal and on-axis location whileshielding the sensor from RF ablation and bending stresses. The tipelectrode is also configured to promote turbulent flow and dispersion ofirrigation fluid for increased thermal transfer from the shell to thefluid and thus with lower flow rates resulting in lower fluid load inthe patient. Fluid, e.g., saline or heparinized saline, can be deliveredto the ablation site from the tip electrode to cool tissue, reducecoagulation and/or facilitate the formation of deeper lesions. It isunderstood that other fluids can be delivered as well, including anydiagnostic and therapeutic fluids, such as neuroinhibitors andneuroexcitors.

With reference to FIGS. 2A and 2B, the catheter body 12 comprises anelongated tubular construction having a single, axial or central lumen18. The catheter body 12 is flexible, i.e., bendable, but substantiallynon-compressible along its length. The catheter body 12 can be of anysuitable construction and made of any suitable material. A presentlypreferred construction comprises an outer wall 20 made of polyurethaneor PEBAX. The outer wall 20 comprises an imbedded braided mesh ofstainless steel or the like to increase torsional stiffness of thecatheter body 12 so that, when the control handle 16 is rotated, theintermediate section 14 of the catheter 10 will rotate in acorresponding manner.

The outer diameter of the catheter body 12 is not critical, but ispreferably no more than about 8 french, more preferably 7 french.Likewise the thickness of the outer wall 20 is not critical, but is thinenough so that the central lumen 18 can accommodate puller members(e.g., puller wires), lead wires, and any other desired wires, cables ortubings. If desired, the inner surface of the outer wall 20 is linedwith a stiffening tube 22 to provide improved torsional stability. Adisclosed embodiment, the catheter has an outer wall 20 with an outerdiameter of from about 0.090 inch to about 0.94 inch and an innerdiameter of from about 0.061 inch to about 0.065 inch.′

Distal ends of the stiffening tube 22 and the outer wall 20 are fixedlyattached near the distal end of the catheter body 12 by forming a gluejoint 23 with polyurethane glue or the like. A second glue joint 25 isformed between proximal ends of the stiffening tube 22 and outer wall 20using a slower drying but stronger glue, e.g., polyurethane.

Components that extend between the control handle 16 and the deflectablesection 14 pass through the central lumen 18 of the catheter body 12.These components include lead wires 40 for the tip electrode 17 and ringelectrodes 21 on the tip section, an irrigation tubing 38 for deliveringfluid to the tip section 15, a cable 48 for the position location sensor46, a pair of puller wires for deflecting the intermediate section 14,and a pair of thermocouple wires 41, 45 to sense temperature at thedistal tip section 15. Glue joint 28 affixes the proximal portion of thecomponents inside the stiffening tube.

Illustrated in FIGS. 2A, 2B and 2C is an embodiment of the intermediatesection 14 which comprises a short section of tubing 19. The tubing alsohas a braided mesh construction but with multiple off-axis lumens, forexample lumens 26, 27, 30 and 32. Each of diametrically opposing firstand second lumens 26 carries a puller wire 36 for bi-directionaldeflection. A third lumen 30 carries the lead wires 40, the thermocouplewires 41 and 45, and the sensor cable 48. A fourth lumen 32 carries theirrigation tubing 38.

The tubing 19 of the intermediate section 14 is made of a suitablenon-toxic material that is more flexible than the catheter body 12. Asuitable material for the tubing 19 is braided polyurethane, i.e.,polyurethane with an embedded mesh of braided stainless steel or thelike. The size of each lumen is not critical, but is sufficient to housethe respective components extending therethrough.

A means for attaching the catheter body 12 to the intermediate section14 is illustrated in FIGS. 2A and 2B. The proximal end of theintermediate section 14 comprises an outer circumferential notch 24 thatreceives an inner surface of the outer wall 20 of the catheter body 12.The intermediate section 14 and catheter body 12 are attached by glue 29or the like.

If desired, a spacer (not shown) can be located within the catheter bodybetween the distal end of the stiffening tube (if provided) and theproximal end of the intermediate section. The spacer provides atransition in flexibility at the junction of the catheter body andintermediate section, which allows this junction to bend smoothlywithout folding or kinking. A catheter having such a spacer is describedin U.S. Pat. No. 5,964,757, the disclosure of which is incorporatedherein by reference.

Each puller wire 36 is preferably coated with Teflon.®. The puller wires36 can be made of any suitable metal, such as stainless steel or Nitinoland the Teflon coating imparts lubricity to the puller wire. The pullerwire preferably has a diameter ranging from about 0.006 to about 0.010inch.

As shown in FIG. 2B, a portion of each puller wire 36 extending throughthe catheter body 12 passes through a compression coil 35 in surroundingrelation to its puller wire 36. The compression coil 35 extends from theproximal end of the catheter body 12 to the proximal end of theintermediate section 14. The compression coil 35 is made of any suitablemetal, preferably stainless steel, and is tightly wound on itself toprovide flexibility, i.e., bending, but to resist compression. The innerdiameter of the compression coil is preferably slightly larger than thediameter of the puller wire 36. Within the catheter body 12, the outersurface of the compression coil 35 is also covered by a flexible,non-conductive sheath 39, e.g., made of polyimide tubing. As shown inFIGS. 2B and 2C, a portion of each puller wire 36 extending through theintermediate section 14 is covered by a nonconductive protective sheath47.

Proximal ends of the puller wires 36 are anchored in the control handle16. Distal ends of the puller wires 36 are anchored in the tip section15 as described further below. Separate and independent longitudinalmovement of the puller wire 36 relative to the catheter body 12 whichresults in deflection of the intermediate section 14 and tip section 15is accomplished by suitable manipulation of the control handle 16.

In the illustrated embodiment, the control handle 16 has a deflectionassembly 60 (FIG. 4) with a deflection arm 62 (FIG. 5), and a rotatableor rocker member 64 (FIGS. 6A and 6B) supporting a pair of pulleys 66(FIG. 7) that act on the puller wires 36 to deflect the intermediatesection 14 and thus the tip section 15. The deflection arm 62 and therocker member 64 are rotationally aligned and coupled such that rotationof the deflection arm 62 by a user rotates the rocker member 64. As therocker member 64 is rotated by means of the deflection arm (representedby line 62), the pulleys 66 are displaced from a neutral position (FIG.3A) with one pulley 66 drawing a puller wire 36 on one side of thecatheter against its anchored proximal end 37 for deflecting the section14 toward that side (FIGS. 3B and 3C). Components such as the leadwires, irrigating tubing and sensor cable can extend through the rockermember 64 within a protective tubing 68. A deflection tension knob 67(FIG. 5) enables the user to adjust the ease by which the deflection arm62 can be rotated. A suitable deflection assembly and control handle aredescribed in co-pending U.S. application Ser. No. 12/346,834, filed Dec.30, 2008, entitled DEFLECTABLE SHEATH INTRODUCER, the entire disclosureof which is hereby incorporated by reference. Other suitable deflectionassemblies are described in co-pending U.S. application Ser. No.12/211,728, filed Sep. 16, 2008, entitled CATHETER WITH ADJUSTABLEDEFLECTION SENSITIVITY, and U.S. application Ser. No. 12/127,704, filedMay 27, 2008, entitled STEERING MECHANISM FOR BI-DIRECTIONAL CATHETER,the entire disclosures of both of which are hereby incorporated byreference.

At the distal end of the intermediate section 14 is the tip section 15that includes the tip electrode 17 and a relatively short piece ofconnector tubing 53 between the tip electrode 17 and the intermediatesection 14. In the illustrated embodiment of FIGS. 8 and 9, three ringelectrodes 21 are mounted on the tubing 53 and the tubing 53 has asingle lumen which allows passage of the tip electrode lead wire 40T,the electromagnetic sensor cable 48, thermocouple wires 41 and 45, andthe irrigation tubing 38 into the tip electrode 17. The single lumen ofthe connector tubing 53 allows these components to reorient themselvesas needed from their respective lumens in the intermediate section 14toward their location within the tip electrode 17.

The tip electrode 17 defines a longitudinal axis 50 and is of a twopiece configuration that includes an electrically conductive shell ordome 51 and internal member or housing 52. The shell is generallycylindrical configuration. It has a narrower open neck portion 56 thatis proximal of a wider distal portion 54. The distal portion has anatraumatic distal end 72 with a flat distal surface and a roundedcircumferential edge. The distal portion has an inner wall 58 thatdefines a generally cylindrical cavity 70 within the shell. The proximalneck portion 56 is aligned and on axis with the longitudinal axis 50. Itis understood that the neck portion 56 need not be narrower than thedistal portion 54. Indeed, the two portions may have the same diameter,except the distal portion 54 is exposed whereas the neck portion 56 iscovered by the connector tubing 43.

The shell 51 is constructed of a biocompatible metal, including abiocompatible metal alloy. A suitable biocompatible metal alloy includesan alloy selected from stainless steel alloys, noble metal alloys and/orcombinations thereof. In one embodiment, the shell is constructed of analloy comprising about 80% palladium and about 20% platinum by weight.In an alternate embodiment, the shell is constructed of an alloycomprising about 90% platinum and about 10% iridium by weight. The shell51 can formed by deep-drawing manufacturing process which produces asufficiently thin but sturdy wall that is suitable for handling,transport through the patient's body, and tissue contact during mappingand ablation procedures. A deep drawn shell is also suitable forelectrical discharge machining (EDM) process to form a large pluralityof through-holes or ports 74 in the distal portion 54 that allowcommunication between the cavity 70 and outside the shell 51. In adisclosed embodiment, the shell has a wall thickness ranging betweenabout 0.002″ and 0.005″, preferably between about 0.003″ and 0.004″, andthe wall has a plurality of holes ranging between about 21 and 140,preferably between about 33 and 60, more preferably between about 33 and57, where a diameter of each hole can range between about 0.002″ and0.010″, preferably between about 0.003″ and 0.004″, and preferably about0.004 inch in diameter.

The internal member 52 is configured to protect and encapsulate thesensor 46 in a distal and centered location within the cavity 70 so thatthe sensor is distal and centered in the tip electrode for optimumperformance. That is, the more centered the sensor is in the tipelectrode and the closer the sensor is to the distal end of the tipelectrode, the more accurate is the data provided by the sensor. In theillustrated embodiment, the entirety of the internal member 52 isreceived in the shell 51.

The internal member 52 has an elongated configuration that is alignedand on-axis with the longitudinal axis 50 of the tip section 15.Advantageously, the internal member has a tubular distal portion 80, abaffle mid-portion 81, a stem portion 82, and a proximal base portion83. Extending through the entire length of the internal member is anon-axis passage 84 to receive the sensor 46 and the sensor cable 48. Ina disclosed embodiment, the tubular distal portion 80 is situatedgenerally in the cavity 70 of the shell, and the baffle, stem and baseportions 81, 82, 83 are situated generally in the neck portion 56 of theshell. That is, the two piece configuration allows the internal member52 to be inserted and received in shell 51, where the tubular distalportion 80 extends in the distal portion 54 of the shell 51, and theproximal remainder (the baffle mid-portion 81, the stem portion 82 andthe base portion 83) extends in the neck portion 56 of the shell 51.

The base portion 83 of the internal member 52 has a circular crosssection (FIG. 9f ) that is adapted for a snug fit with the neck portion56 of the shell to form a fluid-tight seal at the proximal end of thetip electrode 17. The base portion can have a thickness ranging betweenabout 0.003″ to 0.004″.

Distal the base portion is the narrowed stem portion 82 which creates anopen annular gap 88 within the shell 51 between the base portion 83 andthe baffle mid-portion 81 (FIG. 9e ). The width of the stem portion canrange between about 0.090″ to 0.110″.

The illustrated embodiment of the baffle mid-portion 81 includes anequilateral triangular cross-section (FIG. 9d ) with three edges 90spanning between three truncated corners 92 that are in circumferentialcontact with the neck portion 56 of the shell 51. This contactadvantageously enables a snug and on-axis (or centered) fit between theshell 51 and the internal member 52. The triangular cross-section alsoadvantageously creates different axial flow paths or channels 94 forfluid passing into the tip electrode 17. The fluid flowing into thecavity 70 of the shell 51 is separated into distinct flow paths by thebaffle mid-portion 81. These flow paths facilitate dispersion of fluidentering the tip electrode 14 at the base portion. It is understood thatthe cross-section of the baffle portion 81 need not be limited to atriangular configuration, but could be polygonal, includingquadrilateral or pentagonal, so long as multiple flow paths are formedand turbulence is generated without significant drop in fluid pressure.The length of the baffle portion between its distal and proximal end canrange between about 0.050″ to 0.200″.

The tubular portion 80 has a length and an inner diameter so that it canreceive the sensor 46 in its entirety and leave a gap 100 between thedistal end of the tubular portion and a distal end of the sensor. Aconventional sensor has a diameter about 1 mm and a length about 5 mm.The gap 100 is filled by a sealant 101 (FIG. 9A), such as polyurethane,so that the sensor is effectively fixed, sealed and protected in thetubular portion 80. The tubular portion has a length that ranges betweenabout 60% to 90% of the length of the cavity, and preferably about 80%.In an alternate embodiment, the tubular portion is a separate componentfrom the baffle portion and is sealed to the latter. The baffle portion,81, must be made of electrically conductive material, but the tubularportion can be made of plastic such as polyimide. The tubular portionhas an outer diameter that ranges between about 25% and 40% of thediameter of the cavity 70, and preferably about 30% (FIGS. 9B and 9C).These differences in length and diameter advantageously leave a distalgap 102 between a distal end of the shell 51 and a distal end of thetubular portion 80, and an annular region 104 spanning at least thelength of the tubular portion for improved fluid dispersion and flow inthe tip electrode. In the illustrated embodiment, the tubular portion 80has a circular cross-section, although it is understood that thecross-section can be any appropriate shape, including any polygonalconfiguration, e.g., triangular, rectangular, etc.).

At the proximal end of the sensor 46, the passage 84 through theinternal member 52 narrows to form a stop 106 (FIG. 9C) to abut againstthe proximal end of the sensor 46. A junction of the sensor and thesensor cable lies at the stop and the sensor cable extends proximallytherefrom through the reminder of the passage 84 and into theintermediate section 14. The junction between the cable 48 and thesensor 46 is thus hidden inside the internal member 52, surrounded bythe internal member and better protected against cable detachment andbending stresses. This feature also enables an overall shorter length inthe tip electrode allowing for a more maneuverable catheter.

Other formations in the base portion of the internal member includethrough-holes 85, 86A, 86B, 87A, and 87B. A distal end of the irrigationtubing 38 terminates and is anchored in the fluid through-hole 85.Distal ends of the thermocouple wires 41 and 45 are fixed in the hole87A. A distal end of the tip electrode lead wire 40T is anchored in thethrough-hole 87B The tip electrode lead wire 40 energizes the shell 51and at least the base portion 83 of the internal member 52. Distal endof each puller wire has a T-anchor, as known in the art. The T-anchorsare soldered in diametrically-opposing through-holes 86A 86B so that thepuller wires are anchored to the base portion 83 and not a tubing wallwhich can tear. So anchored in the holes 86A 86B the puller wiresprovide the catheter with symmetrical bi-directional deflection of theintermediate section 14. The base portion can also include acircumferential lip 106 at the proximal face as an abutment for aproximal end of the shell 51 so as to maintain the gap 102 between thedistal end of the tubing portion 80 and the distal end of the shell 51.The lip and the proximal end of the shell 51 can be fixedly joined, forexample, by laser welding.

In accordance with another feature of the present invention, the fluidthrough-hole 85 is aligned with the baffle mid-portion 81 such that thehole 85 faces an edge 90 so fluid exiting the hole 85 impinges on theedge 90 and diffuses around the stem portion 82. This alignment betweenthe hole 85 (and the irrigation tubing 38) and the edge 90, combinedwith the annular gap 88 provided by the stem portion 82, enables a flowthat is more uniform and equal in the radial direction through the flowpaths 94 which in turn provides increased turbulence and a more uniformflow rate in the annular space 104 of the cavity 70 and thus moreincreased convective cooling on the shell 51. Irrigation in the tipelectrode is thus more uniform throughout the length of the tipelectrode. The internal member thus effectively counters the tendencyfor the velocity of the fluid entering the tip electrode to carry thefluid to the more distal ports 74 and starve the more proximal ports 74.

The cross-section of the off-axis through hole 85 for the irrigationtubing 38 is elongated, that is, more oval than circular as defined by agreater dimension Y and a lesser dimension X generally perpendicular togreater dimension Y. In the disclosed embodiment of FIG. 9f , thecross-section is elongated with a curvature C, to provide, for example,a kidney-bean or crescent shape cross-section. The present inventionrecognizes that a cross-section which is at least elongated if not alsocurved provides a through-hole that can provide greater fluid flow intothe tip electrode with less interference with the on-axis location ofthe internal passage 84 and the sensor cable 48.

Because the irrigation tubing 85 is flexible, e.g., being made ofpolyurethane, the irrigation tubing 38 readily adapts to the shape ofthe through-hole 85. As irrigation fluid is delivered by the tubing 38into the tip electrode 17 through the through-hole 85, it enters andflows into the annular gap 88 at the stem portion 82 where it isdispersed by the baffle portion 81 and flows into the flow channels 94defined by the edges 90 and corners 92. As the fluid enters the cavity70 between the tubular portion 80 and the shell 51, it further dispersesin the cavity 70 and ultimately leaves the cavity via ports 74. Thecatheter 10 provides better flow and dispersion of fluid within the tipelectrode for improved if not exceptional cooling characteristics duringablation. The tip electrode of the present invention can operate atabout 12 ml/minute or lower for wattage below or above 30. The reductionin fluid-loading on the patient in a five or six hour procedure can thusbe very significant. Moreover, where the flow rate is regulated by aprogrammable pump, the flow rate can even be lower for lower wattage.

In an alternate embodiment of FIG. 10, the internal member 52 includesradial projections or fins 110 that extend outwardly from the tubularportion 80 in a direction generally perpendicular to the longitudinalaxis 50 of the tip electrode. The fins 110 serve to decrease thevelocity of the fluid as it travels distally in the annular region 104of the cavity 70 in the tip electrode. In FIG. 10, the fins are thinannular discs located at intermittent locations, if not equidistant toeach other, along the length of the tubular portion 80. In oneembodiment, the fin diameter increases in the proximal direction, sothat the effect of decreasing fluid velocity is greatest when the fluidfirst enters the annular space 104 in the tip electrode 17 for a moreuniform dispersion of fluid along the length of the tip electrode andthrough all ports 74 in the shell 51 to the exterior of the shell.

Also in the embodiment of FIGS. 10 and 10B, the baffle mid-portion 81has a star-shaped cross-section with a plurality of projections or arms93 that span outwardly in a uniform radial pattern, with ends incircumferential contact with the neck portion 56 of the shell 51, againforming distinct axial flow paths 94 between the arms. However, it isunderstood that the present invention also includes a cross-sectionwhere there is no circumferential contact between the baffle mid portion81 and the neck portion 56, such as illustrated in FIG. 10A. There,different but not necessarily distinct axial flow paths or channels 94are provided, which also facilitate dispersion and flow into the annularspace 104 of the tip electrode.

The entirety of the internal member can also constructed of theaforementioned materials of the shell. And where at least the tubularportion 80 is constructed of a conductive metal, including the palladiumplatinum alloy, the EM sensor is shielded from RF ablation or a stiffplastic such as polyimide. Metal foil can also be used shield the sensoras long as it is electrically connected to the overall electrodehousing. The present invention also includes an alternate embodimentwhere portions of the internal member, for example, tubular portion 80and the housing 52 are constructed of another material, such as plastic,polyimide, polyurethane or PEBAX, to reduce cost.

A length of the tip electrode from a distal end of the shell to aproximal end of the internal member can range between about 2 mm to 12mm, and preferably between about to 3 mm to 10 mm.

The ring electrodes 21 which are mounted on the connector tubing 53 canbe made of any suitable solid conductive material, such as platinum orgold, preferably a combination of platinum and iridium. The ringelectrodes can be mounted onto the connector tubing 53 with glue or thelike. Alternatively, the ring electrodes can be formed by coating thetubing 53 with an electrically conducting material, like platinum, goldand/or iridium. The coating can be applied using sputtering, ion beamdeposition or an equivalent technique. The number of the ring electrodeson the tubing 53 can vary as desired. The rings may be monopolar orbi-polar. In the illustrated embodiment, there are a distal monopolarring electrode and a proximal pair of bi-polar ring electrodes. Eachring electrode is connected to a respective lead wire 40R.

Each lead wire 40R is attached to its corresponding ring electrode byany suitable method. A preferred method for attaching a lead wire to aring electrode involves first making a small hole through the wall ofthe non-conductive covering or tubing. Such a hole can be created, forexample, by inserting a needle through the non-conductive covering andheating the needle sufficiently to form a permanent hole. The lead wireis then drawn through the hole by using a microhook or the like. The endof the lead wire is then stripped of any coating and welded to theunderside of the ring electrode, which is then slid into position overthe hole and fixed in place with polyurethane glue or the like.Alternatively, each ring electrode is formed by wrapping a lead wirearound the non-conductive covering a number of times and stripping thelead wire of its own insulated coating on its outwardly facing surfaces.

The tip electrode 17 is electrically connected to a source of ablationenergy by the lead wire 40T. The ring electrodes 21 are electricallyconnected to an appropriate mapping or monitoring system by respectivelead wires 40R.

The lead wires 40T and 40R pass through the lumen 30 of the tubing 19 ofthe deflectable intermediate section 14 and the central lumen of thecatheter body 12. The portion of the lead wires extending through thecentral lumen 18 of the catheter body 12, and proximal end of the lumen24 can be enclosed within a protective sheath (not shown), which can bemade of any suitable material, preferably polyimide. The protectivesheath is anchored at its distal end to the proximal end of theintermediate section 14 by gluing it in the lumen 24 with polyurethaneglue or the like. Each electrode lead wire has its proximal endterminating in a connector at the proximal end of the control handle 16.

Whereas conventional construction methods build a tip electrode “fromthe outside in,” the present two piece construction allows forconstruction “from the inside out.” That is, the two piece constructionof the tip electrode also allows different order or sequences ofcatheter assembly. For example, the ring electrodes 21 can be mounted onthe connector tubing 53 at a stage separate from the assembly of the tipelectrode 17. The tubing, puller wires, sensor and the thermocouple canbe added to the tip electrode at a later stage or time compared toconventional catheter assembly methods.

Significantly, the two-piece configuration and assembly of the tipelectrode 17 allows for testing, evaluation and inspection of theinterior of the tip electrode before the tip electrode is fullyassembled. One method of assembling the tip electrode includes insertingthe sensor 46 and cable 48 into the central passage 84 of the internalmember 52 so that the sensor is received in the tubular portion 80 ofthe internal member (with the sensor's proximal end abutting the stop106) and the cable 48 extends distally through the central passage 84and out the proximal face of the base portion 83. Thereafter, the sensor46 is sealed within the tubular portion 80 by sealant 101 filling thedistal end the tubular portion 80. Anchoring and attachment of distalends of lead wire 40 for the tip electrode, puller wires 36 andthermocouple wires 41, 45 are then made to the base portion 83 of theinternal member 52 in the respective holes 86A, 86B, 87A and 87B (asshown, for example, in FIG. 9F) by means including T-bar anchoringand/or soldering. A distal end of the irrigation tubing 38 is theninserted to the elongated hole 85 and affixed by adhesive. It isunderstood that each of these anchorings and attachments in the holes inthe base portion forms a fluid-tight seal so that irrigation fluidcannot escape into the connector tubing 53 proximal the tip electrode17. After such stages of assembly have been met, the functionality andintegrity of the tip electrode, including the tip and ring electrodes,the various electrical, component and fluid junctions and connections,and the various fluid-tight seals can be advantageously tested,evaluated and inspected before the shell is received on the internalmember. This feature is another significant advantage over conventionalablation and mapping catheters where testing is done “blind” withouteasy accessibility to the interior of the tip electrode.

After testing of the tip electrode, the shell 51 can be placed over theinternal member 52 centered and aligned by the contact between thecorners 92 of the baffle portion 81 and the neck 56 portion of the shell51. The shell is then attached to the baffle portion via press fit,glue, electrical or laser welding, mechanical deformation, or some othermeans of joining the two parts. The connector tubing 53 is then be slidover the neck portion 56 and connected to a distal end of the tubing 19of the deflectable intermediate section 14.

The preceding description has been presented with reference to certainexemplary embodiments of the invention. Workers skilled in the art andtechnology to which this invention pertains will appreciate thatalterations and changes to the described structure may be practicedwithout meaningfully departing from the principal, spirit and scope ofthis invention. It is understood that the drawings are not necessarilyto scale. Accordingly, the foregoing description should not be read aspertaining only to the precise structures described and illustrated inthe accompanying drawings. Rather, it should be read as consistent withand as support for the following claims which are to have their fullestand fairest scope.

What is claimed is:
 1. A catheter carrying a position sensor, thecatheter comprising: an elongated catheter body; a deflectable sectiondistal the catheter body; a tip electrode distal the deflectablesection, the tip electrode having a central longitudinal axis andcomprising: a shell defining a cavity, the shell having fluid ports; aninternal member in the cavity, the internal member comprising: a distalsegment generally surrounding the position sensor and positioning theposition sensor generally centered in the cavity such that the centrallongitudinal axis of the tip electrode extends generally through acenter of the position sensor, and a baffle segment proximal of thedistal segment and having a polygonal cross-section defining a pluralityof gaps between the baffle segment and the shell; an annular regionextending along the central longitudinal axis of the tip electrodebetween the shell and the distal segment of the internal member, whereinirrigation fluid delivered to the tip electrode travels through the gapsbetween the baffle segment and the shell, is dispersed in the annularregion and passes to outside the shell via the fluid ports.
 2. Thecatheter of claim 1, wherein the distal segment of the internal memberincludes a tubular portion, and the internal member further comprises abase portion proximal of the baffle segment.
 3. The catheter of claim 2,wherein the position sensor is received in the tubular portion of thedistal segment.
 4. The catheter of claim 2, wherein the polygonal crosssection of the baffle segment comprises an equilateral triangular crosssection defining three edges spanning between three corners, the threecorners being in contact with a portion of an inner circumferentialsurface of the cavity, the plurality of gaps being between the threeedges and the inner circumferential surface of the cavity.
 5. Thecatheter of claim 1, wherein at least a portion of the internal membercomprises a biocompatible metal.
 6. The catheter of claim 5, wherein thebiocompatible metal comprises a stainless steel alloy, a noble metalalloy, or a combination thereof.
 7. The catheter of claim 5, wherein thebiocompatible metal comprises an alloy of palladium and platinum, or analloy of platinum and iridium.
 8. The catheter of claim 1, wherein thebaffle segment of the internal member comprises an electricallyconductive material.
 9. The catheter of claim 8, wherein the distalsegment of the internal member comprises a plastic material.
 10. Thecatheter of claim 2, wherein a diameter of the tubular portion is about25% to about 40% of a diameter of the cavity.
 11. A catheter carrying aposition sensor, the catheter comprising: an elongated catheter body; adeflectable section distal the catheter body; a tip electrode distal thedeflectable section, the tip electrode having a central longitudinalaxis and comprising: a shell defining a cavity, the shell having fluidports; an internal member in the cavity, the internal member comprising:a distal segment generally surrounding the posotion sensor andpositioning the position sensor generally centered in the cavity suchthat the central longitudinal axis of the tip electrode extendsgenerally through a center of the position sensor, and a baffle segmentproximal of the distal segment and having a star-shaped cross-sectioncomprising a plurality of arms extending radially outward relative tothe central longitudinal axis of the tip electrode, the plurality ofarms defining a plurality of axial flow paths past the baffle segment;an annular region extending along the central longitudinal axis of thetip electrode between the shell and the distal segment of the internalmember, wherein irrigation fluid delivered to the tip electrode travelsthrough the axial flow paths of the baffle segment, is dispersed in theannular region and passes to outside the shell via the fluid ports. 12.The catheter of claim 11, wherein the plurality of arms of the bafflesegment have ends in contact with an inner circumferential surface ofthe cavity.
 13. The catheter of claim 11, wherein the plurality of armsof the baffle segment have ends that do not contact an innercircumferential surface of the cavity.
 14. The catheter of claim 11,further comprising a least one annular disk on the distal segment. 15.The catheter of claim 14, wherein the at least one annular diskcomprises a plurality of annular disks at different locations along alength of the distal segment.
 16. The catheter of claim 15, wherein aproximal-most annular disk has a diameter greater than a distal-mostannular disk.
 17. The catheter of claim 16, wherein diameters of theplurality of annular disks decrease from the proximal-most annular diskto the distal-most annular disk.
 18. The catheter of claim 11, whereinthe baffle segment of the internal member comprises an electricallyconductive material.
 19. The catheter of claim 18, wherein the distalsegment of the internal member comprises a plastic material.
 20. Thecatheter of claim 11, wherein the distal segment of the internal membercomprises a tubular portion having a diameter that is about 25% to about40% of a diameter of the cavity.